The present invention relates to a technology for developing a seat belt retractor to be installed in a vehicle.
Conventionally, a seat belt apparatus is known, which is structured to protect an occupant in a vehicle by a seat belt (or webbing) restraining the occupant. For example, Japanese PCT International Application No. 2003-507252 (the '252 publication) discloses a structure of a seat belt retractor of a seat belt apparatus in which a spool (or winding shaft) can be rotated for the winding and unwinding of a seat belt by an electric motor.
The technology described in the '252 publication proposes a possibility of using an electric motor to conduct the seat belt winding action of the spool in the structure of the seat belt retractor. When this structure is used for the control of the winding up of the seat belt (the seat belt storing control) in order to prevent the seat belt from being kept in the unwound state, it is desired to reasonably control the seat belt winding action by the electric motor.
Specifically, the original purpose of the seat belt storing control is to prevent a seat belt, which is kept in the unwound state, or a tongue attached to the seat belt from being caught by a vehicle door. A sophisticated (detailed) control can be enabled if the action of the vehicle door catching the seat belt or the tongue is reflected in the control of the seat belt winding action. The inventor of the present disclosure focused attention on the behavior of the vehicle door during the seat belt winding control and came up with a structure capable of changing the mode of the seat belt winding action based on the behavior of the vehicle door.